The present invention refers to a method for determining the bending angle of a work piece that is going to be or has been bent by means of a bending apparatus comprising a punch member and a die member cooperating with the punch member. Moreover, the present invention also refers to an apparatus for determining the bending angle of a work piece that is going to be or has been bent by means of a bending apparatus comprising a punch member and a die member cooperating with the punch member.
It is well known to any person skilled in the art that angular errors can occur in bending a work piece, e.g. a sheet metal work piece, these errors being caused by the non-theoretical behavior of the material. Thus, several distinct methods and apparatuses for measuring the actual bending angle are known in the art.
It is most common in the art to measure the bending angle by means of mechanically operating feelers or probes that are moved towards the bent work piece either from the bottom or from the top until they touch the surface of the work piece. Furthermore, optically operating measuring systems are known in the art that operate with reflected light, with transmitted light or with a laser beam.
Practically all measuring methods known in the art delimit the freedom of bending and the measurable geometry of the parts to a more or lesser degree. Usually, the measuring apparatuses are located in the bending area or are fed to the measuring point from the top of from the bottom. This disadvantage, as well as the fact that the measuring systems known in the art are not too accurate, results in the fact that readily available measuring systems are rarely used.
Thus, it is an object of the invention to provide a method for determining the bending angle of a work piece that is going to be or has been bent that is simple, universal and sturdy to use, yet yields very accurate results within a very short time. Moreover, it is a further object of the invention to provide an apparatus for determining the bending angle of a work piece that is going to be or has been bent that is of simple and sturdy design and that can be universally used, simultaneously being very fast and accurate in operation.
To achieve these and other objects, the present invention provides, according to a first aspect, a method for determining the bending angle of a work piece that is going to be or has been bent by means of a bending apparatus comprising a punch member and a die member cooperating with the punch member and having two bending edges. Once indirectly or directly operating detection members have been provided in at least two different locations on the die member, the detection members are operated to detect the position of at least one leg of the work piece to be bent with regard to the position of the die member and to output position data representing the detected position. Then, the bending angle is calculated in response to that position data and on the basis of previously stored reference data.
Due to the fact that the position of at least one leg of the work piece is determined relative to the position of the die member in at least two spaced apart locations, whereby the bending angle is calculated in response to these measured position data and on the basis of previously stored reference data, the actual bending angle can be determined very quickly and accurately, because, in this case, not the absolute measuring accuracy is important, but rather the reproducibility of the measuring method. As previously stored reference data, for instance measuring data can be used that have been recorded upon bending a reference work piece. Thereby, that reference work piece is bent continuously or step by step, and the measuring data allocated to a certain bending angle are recorded and stored, e.g. in the form of a table.
Preferably, the position of the leg of the work piece is measured both above and below the bending edge of the die member. Thereby, the measuring accuracy can be further increased, particularly in the case of very small or very big bending angles.
According to a second aspect, the present invention provides an apparatus for determining the bending angle of a work piece that is going to be or has been bent by means of a bending apparatus comprising a punch member and a die member cooperating with the punch member and having two bending edges.
The apparatus comprises detecting members for indirectly or directly detecting the position of at least one leg of the work piece relative to the die member and for outputting measurement signals. Means for generating position data on the basis of the measurement signals provided by the detecting members are provided. Further, the apparatus comprises a control and analyzing assembly for calculating the bending angle in response to the position data and on the basis of previously stored reference data, whereby detecting members for indirectly or directly detecting the position are located at different places of the die member.